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Dense Molecular Gas in Galaxies Near and Far

Dense Molecular Gas in Galaxies Near and Far. Yu GAO Purple Mountain Observatory, Nanjing Chinese Academy of Sciences. Talk Outline. 1) Massive Star Formation & Dense Gas GMC Dense Cores , Importance of Dense Molecular Gas in Galaxies, SFR & Dense Gas Tracers, THz/sub-mm

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Dense Molecular Gas in Galaxies Near and Far

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  1. Dense Molecular Gas in Galaxies Near and Far Yu GAO Purple Mountain Observatory, Nanjing Chinese Academy of Sciences

  2. Talk Outline • 1) Massive Star Formation& Dense Gas GMC Dense Cores, Importance ofDense Molecular Gas in Galaxies, SFR & Dense Gas Tracers, THz/sub-mm • 2) HCN in Local Galaxies a) Observations of HCN in 65 Galaxies b)SF Rate vs. Dense Molecular Gas (the FIR--HCN Correlation) • 3) HCN Obs. @ High-z (& GMC cores, FIR—HCN correlation over 10 orders of mag.) • 4) Global SF Law:from dense GMC Cores to Hyper/Ultraluminous Galaxies at High-z (SMGs)

  3. Gas==>>Stars < 1% The least component Content of the Universe

  4. Gas: most important in shaping the CosmicSFhistory

  5. Stars are forming in giant molecular clouds (GMCs)

  6. Diffuse atomic gas（HI）, the gas reservoir for molecular clouds, And the supply for future star formation. PDRs

  7. Gao 2008

  8. The most distant CO images: extended ‘dense’ gas • Mgas= 2 x 1010 Msun • Mdyn~ 6 x 1010 Msun • MBH = 3 x 109 Msun Mdyn ~ Mgas Mdyn = 20 MBH breakdown of relation seen at z=0? extra-nuclear overlap? VLA ---> EVLA Walter et al. (2004) 5 kpc reservoir Perhaps most ‘famous’ QSO:J1148+5251(z=6.42)

  9. 450um contours on 8um image 850um contours on CO image SCUBA: Zhu, Gao, Seaquist & Dunne 2007 CO: Gao, Zhu, Seaquist 2003

  10. CO in VV 114 (Iono et al. 2004, Yun et al. 1994) Note the much compact dense gas traced by CO(3-2) (SMA)

  11. CO Contours overlaid on the optical images (false-color) Gao et al. 1999 Molecular gas density increases as merging advances

  12. 2. Dense gas is the essential fuel for high mass star formation in Galaxies HCN Surveys in 53 Galaxies: Gao & Solomon 2004a ApJS Far-IR, HCN, CO Correlations: Gao & Solomon 2004b ApJ

  13. SFR Dense Molecular Gas

  14. More CO data of ULIGs (Solomon et al. 1997) that Lco > ~ 10^10 K km/s pc^2 Total Molecular Gas Mass

  15. Baan, Henkel, Loenen et al. 2008 HCN,CS,HNC etc. in Local Gals. • Baan et al. (2008) • Kohno 2007, et al. (2003) • Imanishi (2006) • Aalto et al. 2007, 2002, 1995 • Solomon et al. 1992 • Nguyen et al. 1992 • Henkel et al. 1990 • Henkel, Baan, Mauersberger 1991

  16. 3.New HCN@hi-z Obs.(+Literature) Complications: lens, LIR (SFR vs. AGN), CO(1-0)? Source Lfir Lhcn Lco hcn/co mag.f a H1413+117 5.0 3.0 37. 0.08 11 (Solomon+03) F1021+472 3.4 1.2 6.5 0.18 17 J1409+562 17. 6.5 74. 0.09 1 A0827+525 0.25 0.25 .92 0.27 80 B J02396-0134 6.1 <3.7 19. <0.20 2.5 J0413+102 22. <28 159. <0.18 1.3 J0911+055 2.1 <0.6 4.8 <0.13 22 J1635+661 0.93 0.6 3.7 0.18 22 c B1202-072 55. <39. 93. <0.42 1 J1148+525 20. <9.3 25. <0.36 1 J1401+025 0.7-3.7 <0.3-1.5 4-18 <0.08 25-5 M0751+271 2.7 <0.9 9.3 <0.10 17 J02399-0136 28. <46. 112. <0.41 2.5 • 5 detections,1@GBT,3@VLA,1@PdBI (HCN5-4)+4VLA ^limits (Carilli+05). • 4 new searches with VLA (Gao+07), a couple sub-mm galaxies, >50hrs)

  17. Gao, Carilli, Solomon & Vanden Bout 2007 ApJ, 660, L93 ^^^ || ~15hrs VLA, stacking 3 lens components

  18. r.m.s.~19uJy/beam More than 45hrs VLA

  19. Gao, Carilli, Solomon & Vanden Bout 2007 ApJ, 660, L93 13 HCN @high-z

  20. Fit to Galaxies Wu, Evans, Gao et al. 2005 ApJL Fit to GMCs Fit to All Krumholz & Thompson 2007

  21. Resovled Local (FIR-HCN) SF Law ? In Dense Gas (M51 & N6946)

  22. HCN contours on 8um in W3OH FCRAO SEQUOIA

  23. Ma, Gao & Wu 2009 in prep. HCN Dense Gas HCN SFR: IRAC 8um

  24. HCN/HCO+ con. over 8um image HCN/HCO+ > 2 AGN/XDR ???

  25. 4. Star Formation Schmidt Law: from GMC cores to ULIRGs (& high-z) • Schmidt (1959): SFR~density(HI)^n, n=1-3, mostly 2-3 in ISM of our Galaxy. • Kennicutt (1989): Disk-average [SFR~ density(HI+H2)^n] n is not well constrained. ~1-3, wide spread. • Kennicutt (1998): n=1.4 ? Total gas (HI + H2) vs. Dense gas • Better SF law in dense gas?

  26. SFR vs. M_dense(H2): linear correlation

  27. SFR vs. M(H2): No Unique Slope:1, 1.4, 1.7? H2-dominated HI ~ H2 HI-dominated LSB galaxies Gao & Solomon 2004b ApJ

  28. Summary: Dense Gas in Galaxies • Dense Molecular Gas  High Mass Stars • (FIR-HCN linear correlation) SFR ~ M(DENSE) the total mass of dense molecular gas (e.g. gas density >~100,000 cc), linear? • HI  H2  DENSE H2  Stars Schmidt law : HI  Stars Kennicutt : HI + H2 Stars Gao & Solomon: Dense H2 Stars EVLA Q-band local ULIRGs CS(1-0) imaging survey ? From GMC Cores to High-z: Dense GasMassive SF

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